This invention relates to valves used in gas chromatographs (xe2x80x9cGCxe2x80x9d) and more particularly to such a valve that internally blocks fluid communication between ports.
All process GCs include a sample valve. The function of such a valve is to collect a precise volume of a liquid or vapor sample. The components of the collected sample are then separated by the one or more columns in the GC based on some physical or chemical property. The one or more detectors inside the GC are used to sense the separated components as they leave the end of the one or more columns so that component concentrations can be determined.
Referring to FIG. 1 there is shown a simplified block diagram of an on-line process GC 10. GC 10 has a sample extraction and conditioning system 12 which is used to remove a sample from process stream 14. The sample is conditioned to filter contaminants out of the sample before it enters sample valve 16 through sample input port 16a. The valve 16 has also has a sample output port 16b for returning the sample to the sampling and conditioning system 12 and a port 16c for injection of carrier gas. A fixed volume of the sample mixture is injected into the flowing carrier gas stream through port 16a to start the analysis cycle. The function of sample valve 16 is to trap a constant volume of sample in a sample loop 16d and periodically inject the sample into the flowing carrier gas.
The chromatograph column 18 includes a packing, not shown, which may be either a fixed bed of tiny liquid coated particles, tiny porous particles, or the coating on the wall of a capillary tube. The packing is known as the stationary phase and its function is to separate the chemicals in the sample based on some physical or chemical property. The carrier gas sweeps or carries the sample through or past the stationary phase.
GC 10 includes a measuring detector 20 which is located at the outlet of column 18 and produces a signal proportional to the concentration of each component band passing through the detector. GC 10 also includes a reference detector 22 which is exposed to pure carrier gas. Detectors 20 and 22 are connected to vents 21 and 23, respectively. The electrical signals from detectors 20 and 22 are connected to chromatograph controller 24. Controller 24 amplifies, digitizes and integrates the raw electrical signal from detector 20 and produces an output signal when detector 20 is exposed to components leaving the end of column 18 while the reference detector 22 is exposed to nothing but pure carrier gas.
As can be seen from FIG. 1, sample valve 16, column 18, and detectors 20 and 22 are contained in the oven 26 of GC 10. Oven 26 includes a heater 28. The oven ensures that high boiling point liquid samples are vaporized in the sampling valve 16 and also keeps components from condensing.
In addition to being used as sample valves, chromatograph valves are also used as column switching valves. A column switching valve is used to redirect the carrier gas flow during an analysis cycle to load specific components onto different columns for further separation. Column switching valves are also used to reverse the flow of carrier gas through a column and backflush components not of interest off the column to a vent.
Prior art sample and column switching valves usually includes a multiplicity of ports but do not provide internal blocking of fluid communication between one or more pairs of ports. Two examples of such valves are the four port double diaphragm model 44 valve and six port double diaphragm model 46 valve both of which are sold by Applied Automation, Inc. of Bartlesville, Okla. It is desirable to preserve the full functionality of all of the ports in the valve. It is also desirable in a GC to conserve carrier gas.
In many applications where a prior art valve is used, carrier gas should not flow out of a particular port or ports when the valve is in one of its two operating modes but should flow out of that port or ports when the valve is in the other of its operating modes. Blocking the port or ports would not accomplish that result as the port or ports are then blocked for both operating modes. Therefore, prior art valves have included additional hardware external to the valve to regulate the flow out of that port or ports. Such regulated flow is however a waste of carrier gas in that valve operating mode where carrier gas should not flow out of the port or ports.
As was described above, the sample valve along with the column and the detectors are inside of the oven in the GC. The GC oven is of a predetermined size and if external hardware is added to the sample valve to regulate the flow out of a port or ports that external hardware must also reside in the oven. Therefore, the addition of external hardware to the sample valve reduces the room in the oven for additional columns and detectors.
A valve having at least four ports. The valve has first and second operating modes. When the valve is in the first operating mode the at least four ports become at least two pairs of adjacent ports in fluid communication with each other internal to the valve and at least two pairs of adjacent ports not in fluid communication with each other internal to the valve. At least one pair of the at least two adjacent port pairs not in fluid communication with each other internal to the valve when the valve is in the first operating mode separate at least one pair of the at least two port pairs that are in fluid communication with each other internal to valve when the valve is in the first operating mode.
The valve has a first plate which has on its periphery the at least four ports for entry and exit of a first fluid. The at least four ports are in fluid communication with at least four openings in each of the first and second exterior surfaces of the first plate. Each of the at least four openings are associated with a respective one of the at least four ports. The at least four openings in the first exterior surface are blocked when the valve is in the second operating mode.
The valve also has a second plate which has a valve for entry of a second fluid. The second plate also has a first exterior surface which has at least one opening which is in fluid communication with the second plate second fluid entry valve. The valve further has a first diaphragm between the second exterior surface of the first plate and the first exterior surface of the second plate. The first diaphragm pressing against the second plate first exterior surface when the valve is in the second operating mode.
The at least one opening in the first exterior surface of the second plate allows, when the valve is in the second operating mode, fluid communication internal to the valve between all but at least one of the at least two port pairs not in fluid communication with each other internal to the valve when the valve is in the first operating mode.
A process gas chromatograph which has a valve having at least four ports which is embodied as described above, at least one separation column connected to a port of the at least four port valve, and at least one detector connected to the at least one separation column.
A valve having at least 2N ports, where Nxe2x89xa72. The valve also has first and second operating modes. When the valve is in the first operating mode the at least 2N ports become at least N pairs of adjacent ports in fluid communication with each other internal to the valve and at least N pairs of adjacent ports not in fluid communication with each other internal to the valve. At least one pair of the at least N adjacent port pairs not in fluid communication with each other internal to the valve when the valve is in the first operating mode separate at least one pair of the at least N port pairs that are in fluid communication with each other internal to valve when the valve is in the first operating mode.
The valve has a first plate which has on its periphery the at least 2N ports for entry and exit of a first fluid. The at least 2N ports are in fluid communication with at least 2N openings in each of first and second exterior surfaces of the first plate. Each of the at least 2N openings are associated with a respective one of the at least 2N ports. the at least 2N openings in the first exterior surface are blocked when the valve is in the second operating mode.
The valve also has a second plate which has a valve for entry of a second fluid and a first exterior surface having at least Nxe2x88x921 openings each of which are in fluid communication with the second plate second fluid entry valve. The valve further has a first diaphragm between the second exterior surface of the first plate and the first exterior surface of the second plate. The first diaphragm presses against the second plate first exterior surface when the valve is in the second operating mode. the at least Nxe2x88x921 openings in the first exterior surface of the second plate allowing when the valve is in the second operating mode fluid communication internal to the valve between all but at least one of the at least N port pairs not in fluid communication with each other internal to the valve when the valve is in the first operating mode.
A process gas chromatograph which has a multi port valve which is embodied as described above, at least one separation column connected to a port of the multiport valve, and at least one detector connected to the at least one separation column.